1. Field of the invention
This invention in general relates to telecommunication. More particularly, this invention relates to a method for fast identification of colored wires in a multi-wire cable. The wires can be typical electrical wires covered with colored plastic buffers and assembled together in an electrical cable or they can be optical fibers covered with colored plastic buffers and assembled together in an optical fiber cable.
2. State of the Art
Cable identification is a common problem during installation the cable into a telecommunication path. This problem arises with increasing number of the wires in the cable. Conventional methods for cable identification are based on the testing of each individual wires by sending electrical or optical signals in one end of the cable end detecting the corresponding signals at the another end of the cable. This approach is labor intensive because it requires at least two operators to be involved. Besides, a complex specialized technique is required for generating and detecting signals at the both ends of the cable. Also, this technique is expensive and it can only work with certain cables that employ specialized connectors.
The task for cable identification is usually simplified by making the outer layer (buffer) of each wire of different colored plastics. An operator identifies pins and connectors by addressing one color to one connector at the one end of the cable and repeating corresponding sequence of colors and pins at the another end of the cable. This way is acceptable for a limited number of wires in a single cable that can be visually identified. According to a standard TIA-598-A, the number of colors in a cable is limited by 12; they are blue, orange, green, brown, slate (gray), white, red, black, yellow, violet, rose, and aqua. The operator is not able to distinguish more colors in the field conditions. Modern cables, particularly fiber optic cables for local area network (LAN), include more than 100 individual fibers. Secondary buffer of the fibers can be markered by removing the material with a laser, as is disclosed in U.S. Pat. No. 5,111,523 or by adding an extra buffer with a special pattern on it as is disclosed in U.S. Pat. No. 5,796,905. However, the laser ablative technique is too complex and microscopic markers are difficult to recognize in the field because the outer diameter of the buffer can be as small as 0.9 mm.
The conventional colorimetric technique is not acceptable for cable identification due to its complexity and size. A miniature colorimeter disclosed in U.S. Pat. No. 6,157,454 cannot be applied for measuring color of wires in the cable because its light pipe with an axial bore will provide an excess of ambient light leaking around the wire and a flat front aperture. The ambient light is not measured in this calorimeter, and thus, the device will be inaccurate in field conditions with variation of ambient illumination.
It is therefore an object of the invention to provide a device and method for fast and accurate identification of multi-wire or multi-fiber cable.
It is also an object of the invention to provide a device for fast identification of multi-wire or multi-fiber cable that will be inexpensive and portable.
It is further an object of the invention to provide a device and method for fast identification of multi-wire or multi-fiber cable that can be used in field conditions.
According to the present invention, the colored wires or fibers in the cable are identified by illuminating of each colored plastic buffer with a white light and by detecting reflected light with at least three photodectors with attached color filters that are close to standard R, G and B filters. Measured RGB signals are compared by a microcontroller with reference RGB signals that are stored in the memory. Each reference RGB signal from certain buffer is in accordance with a certain identification number, such as number of pin or connector to be connected to wire or fiber that is covered by this buffer. By comparing measured and reference RGB signals the wire or fiber is recognized including the identification of the proper pin or connector. In another embodiment of the method, the plastic buffer is illuminated with a plurality of light emitting diodes (LED) having different colors, particularly those close to primary colors. Light reflected from the buffer is detected by photodetector or plurality of photodetectors and stored in the microcontroller. The wire or fiber is identified in the same way as in previous embodiment, e.g. by comparison measured and reference data.
For both embodiments, the measured and reference data are taken in two steps. Initially, the dark signals are measured from photodetectors without the turning on light sources. These signals are caused by photodetector noise and ambient illumination. In second step, the light sources are turning on and photodetectors"" outputs are measured as light signals. The differences between light and dark signals are actually used for cable discrimination, and thus, the effect of ambient light is minimized.
A number of colors measured by the proposed device exceeds the existing limit of 12 by many folds because with only 8 bit microprocessor the device will have a 24 bit color resolution, or more than 16 million colors. In addition, the device can be inexpensive and portable and very easy to use in field conditions; the identification procedure can be performed by one operator that significantly reduces labor cost.